JPH0456828A - Thin film field effect transistor element array - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thin film field effect transistor element array having a storage capacitance using gate bus lines, particularly for use in active matrix liquid crystal displays.

(Prior Art) Liquid crystal displays are attracting attention as flat panel displays for portable computers and wall-mounted televisions. Among these, the active matrix method, in which an array of thin-film field-effect transistors is formed on a glass substrate and used as a switch for each pixel, is capable of full-color display, so it is expected to be applied to televisions, etc., and is being actively used in various institutions. is being developed. Improving the image quality and definition of this active matrix type liquid crystal display is an important issue, and as a countermeasure to this problem, there is a method of providing a storage capacitor in parallel with the capacitor formed by the liquid crystal. There are two types of storage capacitor structures: one in which the storage capacitor line is provided independently from the thin film field effect transistor, and the other in which the storage capacitor line is provided using the gate bus line of the thin film field effect transistor in the previous stage. The latter structure eliminates the need to provide a counter electrode and a pass line for storage capacitance in the pixel, and can prevent an increase in the number of processes. As a conventional technique using a storage capacitor having a structure using a gate bus line, a structure is known in which a pixel of the next stage is arranged so as to overlap with an extension of the gate electrode of the previous stage. (IDRC'88 P, 155) FIG. 6(a) is a plan view showing one pixel of a thin film field effect transistor element array based on the conventional method, and FIG. 6(b)
is a sectional view taken along line AA' in FIG. 6(a). Figure 6(a)
, 1 and 5.6 are a chromium gate electrode, a chromium drain electrode, and a chromium source electrode, respectively, of a thin film field effect transistor. The chromium source electrode 6 is connected to the pixel electrode 7 via a third contact hole 8c,
The chromium drain electrode 5 is continuous with the chromium drain bus line 4. As shown in FIG. 6(b), the storage capacitor is formed by three types of film: a first insulating film 12, a second insulating film 13, and a surface protection film 14 between the pixel electrode 7 and the third chromium storage capacitor electrode 15. It is formed by sandwiching an insulating film.

(Problem to be Solved by the Invention) Now, in order to avoid flicker, crosstalk, etc. and obtain a high-quality image display, it is necessary to have as large an storage capacity as possible. However, in the configuration shown in FIG. 6(a), when the storage capacitor is increased, the area of the first chromium storage capacitor electrode becomes larger, and the aperture ratio of the pixel portion decreases. Therefore, a bright image with good contrast cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film field effect transistor element array having a storage capacitor structure that reduces the decrease in aperture ratio due to the addition of a storage capacitor and allows a larger capacitance than before.

(Means for Solving the Problems) The thin film field effect transistor element array of the present invention has a plurality of parallel gate bus lines and a plurality of parallel drain bus lines formed in a matrix on a transparent insulating substrate. A thin film field effect transistor is formed near each intersection of the gate bus line and the drain bus line, a pixel electrode is connected to each of the thin film field effect transistors, and a pixel electrode is connected to one of the pixel electrodes. In a thin film field effect transistor element array in which a part overlaps with a part of the previous gate bus line via an insulating film to form a storage capacitor, the pixel electrode and the contact hole formed in the insulating film are a connected second storage capacitor electrode, a first storage capacitor electrode formed in an insulating film, connected to the gate bus line via a contact hole, and sandwiched between the second storage capacitor electrode and the pixel electrode; It is characterized by consisting of.

Further, in a second invention, a plurality of parallel gate bus lines and a plurality of parallel drain bus lines are formed in a matrix on a transparent insulating substrate, and the gate bus lines and the drain bus lines are connected to each other. A thin film field effect transistor is formed near each intersection, a pixel electrode is connected to each of the thin film field effect transistors, and a part of the pixel electrode is connected to the previous stage gate bus line through an insulating film. In the thin film field effect transistor element array, which overlaps the gate bus line and forms a storage capacitor, the gate bus line is laminated with an insulating film interposed between the two adjacent drain bus lines, and the contact A storage capacitor electrode is electrically connected to the gate bus line through a hole, and a storage capacitor electrode is formed in a space sandwiched between the gate bus line and the predetermined storage capacitor electrode, partially overlapping each other with an insulating film interposed therebetween. and a thin film field effect transistor element array having a structure consisting of the thin film transistor and a transparent pixel electrode electrically connected to the thin film transistor.

(Function) According to the thin film field effect transistor element array of the present invention, in the storage capacitor formation section, the pixel electrode, the storage capacitor electrode, and the gate bus line are formed into the same layered structure with an insulating film sandwiched between them. In terms of area, it is possible to obtain a capacity two to three times that of the conventional method.

(Embodiment) FIG. 1(a) is a top plan view showing the structure of a thin film field effect transistor element array having a structure according to a first embodiment of the present invention, and FIG. 1(b) is shown in Figure 1 (a
) is a sectional view taken along line AA'. In Figure 1(a), 1
2 is a chrome gate electrode using chromium as a metal, and 2 is a chrome gate bus line formed at the same time as the chrome gate electrode 1. 4 is a chromium drain bus line, and 5 and 6 are a chromium drain electrode and a chromium source electrode formed simultaneously with the chromium drain bus line 4. 7 is a pixel electrode using ITO. Figure 1(b)
, 8a is a contact hole made continuously in a first insulating film 12 made of silicon oxide (SiO2) and a second insulating film 13 made of silicon nitride (SINx), and 8b is a contact hole made of silicon nitride (SiNx). This is a contact hole formed continuously in a second insulating film 13 made of silicon nitride (SiNx) and a surface protection film 14 made of silicon nitride (SiNx).

9 is a first chromium storage capacitor electrode sandwiched between the second insulating film 13 and the surface protection film 14; 10 is a second chromium storage capacitor sandwiched between the first insulating film 12 and the second insulating film 13; It is an electrode.

By forming a storage capacitor with this structure, it was possible to obtain a storage capacitance value approximately twice that of the conventional one with the same electrode area. Furthermore, when the panel was actually manufactured, a high-quality display was obtained.

A plan view of another embodiment of a storage capacitor using a gate electrode according to the present invention is shown in FIG. 2(a), and AA' in FIG.
A cross-sectional view is shown in FIG. 2(b). In this case, by disposing the third chromium storage capacitor electrode 15 so as to extend below the second storage capacitor electrode 10, the third chromium storage capacitor electrode 15 and the second chromium storage capacitor electrode A storage capacitor is also formed between 10 and 10, thereby realizing an increase in the storage capacitance value. The rest is the same as the first embodiment, so the explanation will be omitted.

As described in the above structure, the thin film field effect transistor element array according to the present invention is shown in FIGS. 1(a) to 2(a).
As shown in b), the value of the storage capacitor can be approximately doubled or more without increasing the area of the storage capacitor.

Furthermore, since the thickness of the insulator between the storage capacitor electrodes can be made thinner than in conventional storage capacitors, the storage capacitance value can be further increased. Furthermore, since the same capacitance value as in the past can be achieved with a smaller area, the effective area of the pixel electrode is expanded and the aperture ratio is increased.

In this example, ITO was used as the transparent conductive film for the pixel electrode, but In2O3 or 5n03 can also be used. Also, as a gate insulating film, 5i0 is used instead of SiNx.
2 may be used. Furthermore, instead of chromium in the gate bus line, drain bus line, and storage capacitor electrode, Ta
It is also possible to use other metals such as , Al, Mo, Ti, etc.

FIG. 3 shows an example in which the present invention is applied to a staggered TFT array, in which (a) is a plan view and (b) is an AA'
FIG. As shown in FIG. 3(a), 1,500 n''-poly-8i films were grown on a transparent glass substrate 11, and drain bus lines 16, drain electrodes 17,
The source electrode 18 and the storage capacitor electrode 19 are patterned. Next, a non-doped poly-8i film is placed on the drain electrode 17 and the source electrode 18 so as to partially overlap with each other.
A film is grown to a thickness of 50 OA and patterned to form an island structure. Furthermore, we have grown 1000 5i02 people across the board,
An insulating film 20 is formed. Next, a contact hole is formed in the insulating film 20 on the source electrode 18, and then 500 ITO films are formed on the insulating film 20 and patterned to form a transparent pixel electrode 21. Furthermore, 1 SiO2
000 people to form the insulating film 22. Next, after forming contact holes in the insulating films 20 and 22 on the storage capacitor electrode 19, a 200OA film of AI is deposited and patterned to form a gate electrode and a gate bus line 23 connected thereto. do.

As shown in the figure, a part of the transparent pixel electrode 21 overlaps with the gate bus line 23 and the storage capacitor electrode 19, and the storage capacitor is formed above and below the transparent pixel electrode 21. By forming the storage capacitor in this manner, the area for forming the storage capacitor can be narrowed, so that a higher aperture ratio can be obtained when the same storage capacitor is formed than in the conventional method.

Incidentally, since such a storage capacitor electrode can be formed simultaneously on the same plane as the source and drain electrodes of the transistor, the number of steps does not increase.

Although an example has been described above in which a storage capacitor is formed between a forward staggered TPT and a front stage gate line, similar effects can be obtained when applied to an inverted staggered TPT or a coplanar TPT.

Further, as shown in FIG. 4, even if a storage capacitor is formed between the gate line of the next stage and the gate line of the next stage, the same effect as described above can be obtained.

Next, the effects obtained by the present invention will be described. As shown in the plan view of FIG. 3(a), in the case where the TFT is of a staggered type, the pixel pitch is 100 m, the wiring width is 10 μm, and the distance between wiring and pixel electrode is 5 μm, the gate forming the storage capacitor The ratio of storage capacity to liquid crystal capacity when the line width is changed. FIG. 5 shows the relationship between the aperture ratio Ap and the aperture ratio Ap.

In FIG. 5, the dotted line shows the case where the conventional method is applied as shown in FIG. 6, and the solid line shows the case where the present invention is applied. As shown in FIG. 5, for example, when the ratio α of storage capacitance to liquid crystal capacitance is 4, the aperture ratio is 56 in the conventional method.
%, whereas in the present invention it can be set to 61%, which shows that when the same storage capacitance is formed, the aperture ratio can be increased.

(Effects of the Invention) As described above, according to the thin film field effect transistor array of the present invention, the storage capacitor can be formed using the gate bus line, and the area of the storage capacitor portion can be reduced, so that the display A display with a larger aperture ratio can be realized without deteriorating quality.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view showing one embodiment of a thin film field transistor element array according to the present invention, FIG. 1(b) is a cross-sectional view showing the storage capacitor section of FIG. 1(a), and FIG. a) is a plan view showing the structure of a conventional thin film field transistor element array, FIG. 2(b) is a sectional view showing the storage capacitor section of FIG. 2(a), and FIG. 3(a) is a plan view showing the structure of a conventional thin film field transistor element array. 3(b) is a plan view showing the storage capacitor section of FIG. 3(a); FIG. 4 is a plan view showing the embodiment of the present invention; FIG. 5 is a diagram for explaining the present invention in detail, and FIGS. 6(a) and 6(b) are a plan view and a sectional view of a conventional example. In the figure, 1... gate electrode, 2... chrome gate bus line, 4... chromium drain bus line, 5... ROM drain electrode, 619. Chromium source electrode, 7...IT
O pixel electrode, 8a...first contact hole, 8b
...Second contact hole, 8c...Third contact hole, 9...First chromium storage capacitor electrode, 1
0... Second chromium storage capacitor electrode, 11... Glass substrate, 12... First gate insulating film, 13... Second
14... Surface protective film, 15... Third chromium storage capacitor electrode, 16... Drain bus line, 17... Drain electrode, 18... Source electrode,
19... Storage capacitor electrode, 20... Insulating film 1.21.
. . . Transparent pixel electrode, 22 . . . Insulating film 2. 23 . . . Gate bus line.

Claims (2)

[Claims] (1) A plurality of parallel gate bus lines and a plurality of parallel drain bus lines are formed in a matrix on a transparent insulating substrate, and a plurality of parallel gate bus lines and a plurality of parallel drain bus lines are formed near each intersection of the gate bus line and the drain bus line. A thin film field effect transistor is formed respectively, a pixel electrode is connected to each of the thin film field effect transistors, and a part of the pixel electrode overlaps with a part of a previous gate bus line via an insulating film. In a thin film field effect transistor element array forming a storage capacitor, a second transistor is connected to the pixel electrode through a contact hole formed in an insulating film.
and a first storage capacitor electrode connected to the gate bus line through a contact hole formed in an insulating film and sandwiched between a second storage capacitor electrode and a pixel electrode. A thin-film field-effect transistor element array characterized by: (2) A plurality of parallel gate bus lines and a plurality of parallel drain bus lines are formed in a matrix on a transparent insulating substrate, and a plurality of parallel gate bus lines and a plurality of parallel drain bus lines are formed in the vicinity of each intersection of the gate bus line and the drain bus line. A thin film field effect transistor is formed respectively, a pixel electrode is connected to each of the thin film field effect transistors, and a part of the pixel electrode overlaps with a part of a previous gate bus line via an insulating film. In a thin film field effect transistor element array forming a storage capacitor, the gate bus line is laminated in a region between two adjacent drain bus lines with an insulating film interposed therebetween, and A storage capacitor electrode electrically connected to the gate bus line, and a storage capacitor electrode formed in a space sandwiched by the gate bus line and the storage capacitor electrode, partially overlapping each other with an insulating film interposed therebetween, and with the thin film transistor. A thin-film field-effect transistor element array with a structure consisting of electrically connected transparent pixel electrodes.